Yes, 2.6.1 (and 2.6.1.1) have a conflict with BP Group Hierarchy. The problem is caused by the addition of the autoloader check in bp-loader.php because BPGH instantiates its class before BP knows if the groups component is active or not. The short term fix is, unhappily, to change bp-loader.php. Comment out the line that reads return (add a // before return) here:https://github.com/buddypress/BuddyPress/blob/master/src/bp-loader.php#L621